SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'd6b4ef712fe651b36a3d365887c2584aefddfac9d549b38b4e1e24cd5c4e6c47' 
  AND token = 'zUjNM4PpDIe6TPw91ZyB8/7GtiALhguWJCMUpyNSgOs=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00022

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}